Sleeping with my best mates prized daughter...help?

I'm looking for some man to man advice. I'm a 54yr old part time builder. I never married, couldnt be doing with being shackled. Basically I hang out with a group of men, some of them married, some of them not. I have a bit of a rep for being a 'stud' and have no problems with the ladys, i find they dig the burly builder rough look. I dont mind admitting, i have often bedded 2 / 3 different woman in a month, from aged 25 - 50yr olds. However, one of the buddies from our group has this 'prize filly' of a daughter. Shes real smart, shes just started in university, doing a real challenging degree course. Shes the apple of her old man's eye, and he never stops boasting about her. Shes a looker, and he refuses to acknowledge she aint no little girl anymore and that she could have been 'around the block'. He sent me up to her apartment (2 hrs drive) to carry out some repairs. The sight of her huge rack and skimpy shorts really got me in the mood. It wasnt long before she was showing me some hot action, and my can this girl r.de. Im actually almost left for dead after 2 nights with daddy's little tiger. Shes 24yrs old and man, i cannot get her out of my head and i've hardly gone down (if you know what i mean). However, its going to be awkward this weekend as its her old mans birthday and shes up. How do i handle this